Questionable Parts (hardware)

[Philippe]

Having completed five DIY guitar effects over the past few months, I've discovered a manufacturing quirk & was wondering if others have encountered it. This pertains to those Alpha potentiometers that have pretty much become standard fare for the majority of these do-it-yourself projects.

Out of eight Alpha potentiometers ranging from 10K to 100K, I've had three that I would consider defective, either from lax design or manufacturing defect. Two had wobbly shafts. I discovered this while mounting the knob(s). At first I thought the brass inner sleeve of the knob was out of round. This was not the case as it turned out there was play between the pot bushing & shaft itself. The other pot was peculiar in that it only worked properly backwards (i.e. going counterclockwise). Initially I thought it was my error in mis-soldering the leads to lugs 1 and 3. After reversing them, the pot still operated 'backwards'.

All of which brings me to this apparent conclusion...upon further inspection & dismantling of one Alpah pot & unlike some of the more expensive, higher quality potentiometers (e.g. CTS, Bourn et al) the shafts on the Alphas are not secured within the casing itself. They simply pivot within the bushing leaving room for slop. As for the backwards operating pot, this was an obvious manufacturing/QA issue.

Unfortunately, a lot of times this kind of stuff gets discovered only after everything is assembled & to R&R an otherwise properly functioning potentiometer can be a major pain in the ass. Fortunately there is beer.

My questions & points...have any of you come across this & is it feasible to consider using better grade potentiometers? The Allesandros run about $15.00 apiece & the CTS pots cost around $8.00-9.00. Granted it makes for a higher project cost but in the long-run we perhaps end up with a better-made box?

This low-end overseas manufacturing (e.g. Taiwanese) where quality control & design are oftentimes an oxymoron can make for an exasperating project. I recall reading an article by R. Keen where he is even questioning the longevity of those Taiwan blue 3PDTs. So far I haven't had any problems with them & if they are good for 5,000 'clicks' , well that's about 3-4 years based on my specific usage. The Alpha potentiometers are another story...reasonably-priced crap but you pay a price in the overall operation & quality of your final results.

[JKowalski]

I haven't had any of the problems you are describing with any of my 50+ 55 cent alphas. They have lasted me a good two years... Maybe I am just lucky?

There's always the option of moving up in quality, but considering the price of most of the "high grade" pots I can't imagine myself ever doing it. 50 cents is worth the added risk of having to replace them, IMO

I also like the ability to order a ton of potentiometers in every size and have them available at all times for designing and whim projects, you just can't do that with high grade pots unless you have plenty of money to burn  

[Joe]

Never had too many problems, except forgetting to break the tab off or using too much torque when installing. Too much pressure can screw them up.

[ianmgull]

I've had problems with the cheap Alphas. There have been a couple where the resistance will suddenly drop to zero if apply a bit of side to side force on the shaft. It is as if the wiper breaks connection with the resistive element briefly.

[Toney]

Yeah, my latest batch of Alphas seem like a step down in quality.
The have replaced the back plate with some kind of ultra crappy silver colored light-weight alloy.
(previously less crappy gold color alloy)

[darron]

i don't understand what you mean by only working backwards.

if there's anything to upgrade in a pedal, it's often the electromechanical stuff, so if you think it's worth it to you to sink the extra cash into nicer pots and enclosures etc. then i say go for it. you'll be happier knowing you did the best you could. however, it practically won't be any better in most cases, so if you're trying to save a dollar (yen? euro?) then don't bother.

i've never really had any problems with alpha pots. we used to buy them in the thousands and per 1000 about 6 would be smashed and have obvious problems by looking at them. the tolerances aren't at all fantastic, IE a 100K pot could sometimes read up to 130K, but the other side of the wiper always goes to zero and that's more important end of the taper i think.

a lot of people have problems with pots going intermittent when heat can EASILY damage them. this can make the wiper do all sorts of crazy things and have you scratching your head for ages. this especially happen when people use the PCB mount pots and solder wires into the little holes that LOOK like they are supposed to support a hookup wire.

if alpha pots are indeed going bad, then i suppose i'll be moving away from them, but so far they have been good and conveniently stocked everywhere.

regarding what Toney said, as long as I can remember Alpha pots have always come in the gold colour and the silver colour and whatever the distributor sent you was just random luck, it seemed. maybe i haven't seen this new dodgy batch yet, but i'm in melbourne too. where do you buy your stuff from Toney?

i do hate that sticky crap that they always have on them though! when you spend hours measuring hundreds of them and snapping the tabs off you feel like, i dunno, you shook hands with a hooker who bathes in beer?... *cough*....

[Toney]

Altronics in Dandy Rd and Futurlec.
Seems that these newer 'lite' ones are fairly recent. They are noticeably less weighty. Whether that translates to a drop in performance we'll see. They certainly feel more cheesy.
+ 1 on never having any major issues with Alphas except for overheating.
They are great and then they break. 

[darron]

oh no! lol... that's where i go too for most of my stuff too... then again i need to get my stuff from many suppliers:

altronics - caps/resistors etc
jaycar - some ICs, knobs
RS components australia - enclosures
small bear electroincs - jacks, 3pdts, odds
dick hole smith - germanium diodes, sometimes knobs
rockby electronics (around the corner from altronics) - trimmers, some odds
payal dandenong - excellent indian food
grandma - socks undies etc.


i guess we'll be right, they aren't quiet the monopoly on the market

[Toney]

oh no! lol... that's where i go too for most of my stuff too... then again i need to get my stuff from many suppliers:

payal dandenong - excellent indian food
grandma - socks undies etc.

 

Yeah I'm pretty much with you on that list.
'Cept for Grandma and I get over to Carnegie for my Korean food fix. Just discovered how delicious it is in the past few years. Mucho-belcho-hotto though. (You gotta love chillis).
Rockby are great for the obscure stuff but mmmm-mmm they know it and charge accordingly.
Checkout Dick (head) Smith for big quick-stock discounts at the moment. Good to stock up on those yellow MKT caps for cheap etc.